Kess always wanted to follow in the footsteps of her brother, Grey. She grew up in Kalm, her parents owned the local inn. Her childhood was relatively normal, but she always felt as though something was missing. When she was fifteen, Grey left to join Soldier. Many teenagers in the town had dreams of becoming as powerful and famous as the Great Sephiroth. However, most of them were shipped to the war at Fort Tamblin in Wutai. Grey did a tour and then returned to Junon on leave when Kess finally arrived on the scene. The two siblings reunited, Grey introduced Kess around the city and to members of his squadron. But within a week of her arrival, they were shipped out once more. Kess would never see her brother again.

She would eventually receive a letter about his unfortunate death and less than a month later, the news of the destruction of Kalm reached her. Devastated, Kess sought a means to end the pain she felt, but her plunging into the Junon Sea was unsuccessful in her goal. She was revived and taken to Midgar, being placed in Deepground and under the watchful eye of Professor Hojo.

She regained her strength and then training began. Her peers were other Soldiers, many had been injured during the war. They were cybernetically enhanced and sent back out into the world to complete secret missions for the Company. On one such mission, Kess discovered what had truly happened in Kalm. Furious at the lies she had been told about it being an accident, she went AWOL. She turned up in Cosmo Canyon seeking Avalanche and instead found an ally in Ashe Kincaid. Together, they made plans to head to Midgar and join the ranks of the reborn Avalanche.